Well, if she sent you $1184 and the cel she wants 
is $1000, I don't see why you shouldn't give it 
to her- Yes, it sucks that she can't pay for the 
others, but if she has given you $1000 and the 
cel she wants is $1000, you got what you wanted 
for it. I don't see any reason to give her the 
$800 cel instead, it's not like she only gave you 
$800. As for whether you keep the difference - 
$184- that seems pretty severe- maybe keep $50 or 
$100 for your trouble on the other cels.  
Or, just refund the money (again, I don't think 
it's unreasonable to keep a little as something 
of a service charge if you have done everything 
right on your end) and refuse to do business with 
her again.